Priority is claimed from French application no. 01 06703 filed May 22, 2001.
The invention relates to composite electrical insulators for substations or for medium or high voltage lines and fitted with optical fibers, and more particularly the invention relates to a composite electrical insulator comprising a support rod generally of composite material, two metal end-fittings each forming a socket in which a corresponding end of the support rod is inserted, at least one optical fiber placed on the outer periphery of the support rod, and an insulating outer coating surrounding the support rod and covering the optical fiber which has at least one end guided to the outside of the insulator through an end-fitting.
Patent document EP-0 926 516 discloses such a substation composite electrical insulator. In that known insulator, the optical fiber is stuck to the outer periphery of the support rod and each end of the optical fiber is guided to the outside of the insulator through an end-fitting via an annular groove formed in the outside surface of a cylindrical portion of the end-fitting surrounded by an outer annular portion of the end-fitting and then by a duct passing through the annular portion and leading to outside the end-fitting. Such an arrangement is complicated to implement, gives rise to problems of sealing the insulator along the optical fiber, and is not suitable for insulators of small diameter, such as line insulators.
The object of the invention is to remedy those drawbacks.
To this end, the invention provides a composite electrical insulator comprising a support rod generally of composite material, two metal end-fittings each forming a socket in which a corresponding end of the support rod is inserted, at least one optical fiber placed on the outer periphery of the support rod, and an insulating outer coating surrounding the support rod and covering the optical fiber which has at least one end guided to the outside of the insulator through an end-fitting, wherein said end of the optical fiber is guided through the end-fitting by a groove formed in the inside surface of the socket of the end-fitting, said groove opening to the outer periphery of the support rod, and by a duct extending said groove and opening to the outside of the end-fitting. Consequently, in the insulator of the invention, the optical fiber is guided in part between the rod and the metal end-fitting, thus making it possible to design an end-fitting having a small outside diameter. The groove and the duct can easily be made at particularly low cost by casting without any machining. The insulator is easily sealed by plugging the duct with an insulating gel or with adhesive.
In a particular embodiment of the insulator of the invention, the groove is rectilinear and extends along the longitudinal axis of the socket of the end-fitting which can thus be fixed onto the support rod by mechanical crimping. The duct forms a bend so as to open out through a side of the metal end-fitting, with the radius of curvature of the duct being adapted to the mechanical characteristics of the optical fiber. The groove flares towards the outside edge of the mouth of the socket in the end-fitting so that the optical fiber which is generally wound helically around the support rod can be inserted into the groove without being damaged. A gasket of adhesive surrounding the rod is placed against the outside edge of the mouth of the socket in the end-fitting in order to close the groove. As a result, the outside coating, generally made of elastomer, does not penetrate into the groove while it is being applied to the support rod, e.g. by injection molding. This eliminates any risk of the optical fiber being damaged.